HA on Rasp Pi stopped working, WebSocket NWError 0, Eero router shows it connected

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My Raspberry Pi-powered Home Assistant had been working great for the last 2.5 years, but suddenly a week ago my HomeKit stuff can’t control my Z-wave light switches. I have rebooted the HA device a few times, and I can see it connected via WiFi to my Eero router. But the Home Assistant iPhone app shows that it can’t connect to the server.

I haven’t had a Home Assistant-related thought in 2.5 years while it was working, I don’t even know where to begin to fix this. Searching for the error code hasn’t helped.

(tried this one for the NSURLErrorDomain -1004 error, but turning off that option on my phone didn’t help)

Thank you for suggestions for what I should do.

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IMG_885BD537D174-11228×1278 143 KB

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btw, I can ping the Raspberry Pi

wes@WesiMac ~ % ping 192.168.4.201
PING 192.168.4.201 (192.168.4.201): 56 data bytes
64 bytes from 192.168.4.201: icmp_seq=0 ttl=64 time=72.013 ms
64 bytes from 192.168.4.201: icmp_seq=1 ttl=64 time=2.362 ms
64 bytes from 192.168.4.201: icmp_seq=2 ttl=64 time=2.999 ms
64 bytes from 192.168.4.201: icmp_seq=3 ttl=64 time=2.464 ms